There are still a lot of misconceptions floating around about barrel "break-in".
One of such is that it will make your rifle more accurate. This is hogwash!!
The real purpose behind shoot/clean, shoot/clean is to condition the barrel
for future ease of cleaning.
This it does accomplish.
For custom barrels, it is good to follow the manufacturers protocol.
For factory barrels, I like to shoot 1, clean [for 5 shots], then shoot 3, clean for
an additional dozen, then shoot 5, clean for 15 more.
As far as accuracy goes, you get what you buy, more or less. Factory barrels
can be surprisingly accurate, or can be dismal. [they tend to be pretty good overall, though.]
I have a borescope, and have looked through a fair number of barrels.
The way a barrel looks inside MAY give a clue as to how it will shoot, but even that is
far from definitive.
I have a factory rifle that looks rather rough through the borescope.
But it is a very accurate rifle, and does not foul badly.
I recently took a look down the barrel of a well-respected [for accuracy] rifle make from Europe.
There was a serious looking flaw in one land about 1/3 of the way back from the muzzle.
This rifle shoots moa with most of what it is fed, but will begin to copper foul at the flaw after 20+ shots.
Then accuracy starts to deteriorate.
Clean it up....back to moa or better.
The owner has chosen to leave well enough alone, just keep it clean.
However, many shooters are plenty happy just to clean the firearm initially before they shoot it.
Then take it out and shoot a box or two of ammo.
If it works for them, I'm OK with that.
Regards, Dave.